The invention relates to a method and arrangement for controlling the local operation of a mobile station. A mechanism for restricting connection of a mobile station to a cell will be disclosed as one embodiment of controlling the local operation. The invention also relates to a mobile station, data base, subscriber register, location updating method and handover method.
In cellular mobile communications systems, a mobile station may roam freely within the area of the mobile communications network and connect to the base transceiver station signal received best at a given time. Usually, all base transceiver stations provide substantially similar services for the mobile stations in a network. Some base transceiver stations can, however, be defined to provide a certain special service for all mobile stations of the network, e.g. call charges below the normal tariff. The base transceiver station broadcasts a message on such a special service on its broadcast control channel (BCCH), whereby mobile subscribers in the area note that they are within a special service area of the network and may take advantage of this service.
FIG. 1 shows a simplified block diagram of the structure of the pan-European GSM system. The mobile station MS is connected via a radio path to a base transceiver station BTS; in the case shown in FIG. 1 to the base transceiver station BTS7. An idle mobile station MS receives transmission from the base transceiver station selected by it. A base station subsystem BSS comprises a base station controller BSC and base transceiver stations BTS under its control. Usually, there are several base station controllers BSC under a mobile services switching centre MSC. The mobile services switching centre MSC is connected to other mobile services switching centres, a gateway mobile services switching centre GMSC and possibly to an intelligent network IN. The GSM network is connected to other networks through the gateway mobile services switching centre GMSC, such as the public switched telephone network PSTN, another mobile communications network PLMN, ISDN network or intelligent network IN.
The subscriber data of the mobile station MS are stored permanently in a home location register HLR of the system, and temporarily in the visitor location register VLR in the area of which the mobile station is located at a given time. The location information of the mobile station MS is stored in the visitor location register VLR with an accuracy of a location area LA. The geographical area controlled by the visitor location register is divided into one or more location areas LA, within each of which the MS may roam freely without notifying the VLR. Within each location area there may be one or more base transceiver stations BTS in operation.
Base transceiver stations BTS continuously broadcast information on themselves and their environment on their broadcast control channel, e.g. the cell identity CI, information on neighbouring cells and the location area identifier LAI. On the basis of the LAI, the mobile station MS receiving broadcast transmission from the base transceiver station BTS knows in which location area LA it is at a given time. If the mobile station MS notices, on changing the base transceiver station BTS, that the location area identifier LAI of the base transceiver station has changed, it sends a request for location updating to the network. The location area of the mobile station MS is updated to the visitor location register VLR in the area of which the mobile station is at a given time. Information on the VLR covering the area where the MS is located is transmitted to the home location register HLR.
The mobile station MS continuously measures signals of the base transceiver stations BTS located nearest to the cell within which the mobile station is located e.g. to determine the base transceiver station providing the best signal and to be prepared for a possible handover. The mobile station identifies the neighbouring cells it is to monitor on the basis of the information on neighbouring cells transmitted by each base transceiver station on its broadcast control channel. For example, in the GSM system the mobile station MS can simultaneously measure the signal level and/or quality of a maximum of 32 other base transceiver stations in addition to the serving base transceiver station. When roaming within the mobile communications network, the mobile station MS usually connects to receive the base transceiver station BTS having the strongest signal. Thus an effort is made to set up a call terminating to a mobile station MS or a call originating therefrom primarily through this base transceiver station BTS.
In mobile communications systems, location information on the MS is needed for routing incoming calls and for other network services. FIG. 2 of the attached drawings shows by way of example location updating triggered by the mobile station MS as a signalling chart. The mobile station MS requests a signalling channel from the base transceiver station BTS for location updating and sends a request for location updating (message 21) on the assigned channel. The request is transmitted to the mobile services switching centre MSC. The mobile services switching centre MSC forwards the request for location updating to the visitor location register VLR in message 22. In step 23, the authenticity of the subscriber is verified (known as authentication) e.g. to control the access to the network and to prevent abuse. In authentication, information stored in the network is compared with information stored in the mobile station MS. After a successful authentication the new visitor location register VLR transmits a message 24 on location updating to the home location register HLR of the mobile station. The home location register HLR acknowledges location updating by sending the necessary mobile subscriber data (message 25) to the visitor location register VLR. In step 27, information on the protection algorithm that will be used is transmitted to the mobile station MS. The visitor location register VLR informs of completion of location updating in message 28. The mobile services switching centre MSC forwards this message to the mobile station MS in message 29. Messages 28 and 29 also include the new temporary mobile subscriber identity TMSI assigned to the mobile station MS by the visitor location register VLR. After completion of location updating, the signalling channel used is released. In addition to the location updating signalling described above, the visitor location register VLR, if necessary, also inquires the identity of the mobile station and requests authentication keys of the mobile station and other necessary subscriber data either from the previous visitor location register of the mobile station or from the home location register HLR.
A problem associated with the above-mentioned embodiment for providing special services in a network is that both base transceiver stations providing special services and base transceiver stations providing standard services have to serve all the mobile stations entitled to use the network substantially in the same way. Hence it is not possible to provide tailored special services to which other mobile stations are not entitled for individual mobile stations or for a mobile station group. A problem associated with prior art mechanisms of the embodiment in which controlling of the local operation comprises restricting connection to a cell is that the restriction covers the whole network, and thus the mechanisms are not suitable for locally restricting the use of a mobile station.
An object of this invention is to create and utilize subscriber-specific or subscriber-group-specific localised service areas. Localised service areas allow to provide some locally tailored special service, e.g. call charges below the normal tariff. Alternatively, or additionally, connection of a mobile station to a network can be restricted locally.
This new kind of controlling of local operation of mobile stations is achieved with methods and apparatuses, which are characterized by what is disclosed in the appended claims. According to the invention, a mobile-station specific list of special cells is drawn up of selected network cells, and the operation of the mobile station is controlled on the basis of said list of special cells, e.g. connection of a mobile station to a network is restricted.
The invention also relates to an arrangement comprising means for processing location updating. According to the invention, the arrangement is characterized in that it comprises a list of special cells drawn up for a mobile station, means for processing said list of special cells, and means for controlling the operation of the mobile station on the basis of said list.
The invention further relates to a data base, which, according to the invention, is characterized in that it comprises a list of special cells drawn up for a mobile station, the list comprising information on localised service cells of the mobile station. This data base can be used for providing locally tailored services or for locally restricting connection of a mobile station to a network.
Furthermore, the invention relates to a mobile station which is arranged to send a request for location updating. According to the invention, the mobile station is characterized in that it comprises means for storing a list of special cells and means for utilizing the stored list of special cells. Said utilization may comprise e.g. a message provided for the user that the mobile station is within a localised service area. Utilization may also mean that the mobile station is arranged to connect only to the cells on the list of special cells.
The invention further relates to a location updating method, in which a request for location updating is sent to the network from a mobile station in order to update location information of the mobile station. The request for location updating is transmitted to a visitor location register in order to update the location area of the mobile station, and a message on location updating is sent from the visitor location register to a home location register in order to update the location information of the mobile station. Location updating is carried out in the home location register and an acknowledgement message on completion of location updating is sent by the home location register to the visitor location register, and location updating is carried out in the visitor location register, and a message on completion of location updating is sent to the mobile station. According to the invention, the location updating method is characterized in that a service request is sent from the visitor location register in order to ask for information on special cells of the mobile station, and this information on special cells is sent to the mobile station.
Furthermore, the invention relates to a handover method, characterized in that when a mobile station roams from one cell to another, the old cell and/or the new cell being a special cell, information on changes is transmitted to the mobile station already in the handover command.
The invention is based on the idea that a special service area is defined for a mobile subscriber by drawing up a list of certain network cells, i.e. special cells, for the subscriber. The list can be utilized in a mobile station or in a fixed network. In the present application such a special service area is referred to as LSA (Localised Service Area).
In the method of the invention the list of special cells is stored for the mobile subscriber in a data base, preferably in the home location register or in the data base of the intelligent network. The list contains network cells defined e.g. as preferred cells, in which some special service, e.g. call charges below the normal tariff, is provided for the mobile station in question. According to one embodiment, connection of a mobile station to a network can be totally restricted outside preferred cells. Decisions on providing a special service and/or restricting connection to a cell can be made in a mobile station or in a fixed network or in both of these.
In usual cases only a few special cells are defined for each mobile station, and hence this list can be stored e.g. in the SIM card of the mobile station. In theory, however, a mobile subscriber could have dozens or even hundreds of special cells, and thus instead of the SIM card or in addition to it the list of special cells could be maintained in connection with location updatings of the mobile station. If changes are noticed in the information on the special cells of the mobile station, e.g. when the mobile station sends a request for location updating to the network, in addition to the location updating method of the prior art, the list of special cells stored, or the part of the list of special cells related to the location area, is fetched from the data base for the mobile subscriber performing the location updating, and the information on special cells that was fetched is transmitted to the mobile station e.g. as an USSD service, short message or as attached to the location updating signalling. One possible solution for this is the method known as SIM Data Download, defined in the GSM recommendation 11.14 of ETSI. The mobile station stores the updated list in its memory. When roaming within the mobile communications network, the mobile station can compare the identifier received from the base transceiver station with the stored list. If the identifier of the base transceiver station corresponds (or does not correspond) to the identifier on the stored list, the mobile station can inform the user of this, e.g. with a tone or a text on the display of the mobile station. According to one preferred embodiment of the invention, the mobile station does not need to compare the identifiers itself to find out whether changes have occurred in the special cell situation, but it may receive information from the base transceiver station during the call that the special cell situation is changing, or has changed. In this case, the mobile station can react to the change in the information on special cells on the basis of some criterion set to the mobile station. For example, it may cut off a call which cannot be maintained in the LSA area.
The methods and systems of the invention have the advantage that in a public mobile communications system, special services reserved only for certain subscribers can be arranged to certain cells, e.g. call charges below the normal tariff, or other supplementary services which are not supported in the areas of all the base transceiver stations.
One further advantage of the inventive solution is that it is based on the standard cellular structure of a mobile communications network.